As a conventional technology for forming a thin film having gas barrier properties (hereinafter, also referred to as a gas barrier thin film), a plasma chemical vapor deposition (CVD) method is available (see, for example, Patent Literature 1). Patent Literature 1 discloses a method of laminating a gas barrier thin film which contains an inorganic oxide as a main component, on the inner surface of a plastic container using an organosilicon compound as a raw material. However, the method for forming a thin film by a plasma CVD method is such that at the time of thin film formation, plasma damages the film surface, so that compactness of the film is prone to damage, and may become an obstacle to an enhancement of the gas barrier properties, or to securement of the adhesiveness of the thin film. Furthermore, since a plasma CVD method ionizes a raw material gas by decomposing the raw material gas with plasma, and causes ions that have been accelerated by an electric field to collide with the surface of a plastic container to form a thin film thereon, the method essentially requires a high frequency power supply and a high frequency electric power adjusting apparatus, and there is a problem that a large amount of money is required for the equipment cost.
In order to solve this problem, the Applicant of the present invention has disclosed a technology for forming a gas barrier thin film on the surface of a plastic container using a method of decomposing a raw material gas by bringing the raw material gas into contact with a heating element that has been caused to generate heat, and depositing the chemical species thus produced as a thin film on a base material directly or after a reaction process in a gas phase, that is, a CVD method which is also called a heating element CVD method, a Cat-CVD method or a hot wire CVD method (hereinafter, in the present specification, referred to as a heating element CVD method) (see, for example, Patent Literature 2 or 3). Patent Literature 2 discloses a technology of forming an AlOx thin film or a SiOx thin film as an oxide thin film by using a mixed gas with a non-pyrophoric raw material and ozone as a raw material gas. Patent Literature 3 suggests a technology related to a heating element CVD method by which, for example, a hydrogen-containing SiNx thin film, a hydrogen-containing DLC thin film, a hydrogen-containing SiOx thin film, or a hydrogen-containing SiCxNy thin film can be formed by combining plural gases as raw material gases.
As a method for forming a gas barrier thin film, in addition to those, a technology for forming a SiN (silicon nitride) or SiON (silicon oxynitride) thin film by a heating element CVD method on the surface of a base material formed from a thermoplastic resin, using a nitrogen-containing gas and a silane-based gas as raw material gases, has been disclosed (see, for example, Patent Literature 4). Furthermore, as a method for forming, not a gas barrier thin film, but a thin film by using a heating element CVD method, for example, a technology for forming a thin film of a chemical species that has been generated by bringing a raw material gas into contact with a heating element that is heated to 800° C. to 2000° C., on a substrate that is heated to 150° C. to 400° C. by a thermal CVD method, has been disclosed (see, for example, Patent Literature 5). Patent Literature 5 discloses a method of depositing a thin film using a gas obtained by mixing plural gases. Furthermore, a technology for enhancing gas barrier properties by means of a SiCN film, using a silazane-based raw material gas, has been disclosed (see, for example Patent Literature 7).